Mechanism and properties of novel ionic liquid for zin 2025 Green and Smart

The innovative application of choline chloride and para-toluenesulfonic acid (ChCl–pTSA) as a novel leaching agent for zinc (Zn)-containing dust sludge was investigated. The selective Zn leaching mechanism of the dust sludge was revealed using Fourier-transform infrared and X-ray photoelectron spectroscopy (XPS) and verified using molecular dynamics simulations. The leaching results showed that under conditions of a liquid-to-solid ratio of 8:1, leaching time of 15 min, and leaching temperature of 40 °C, the leaching rate of Zn, Fe, and Al was 92.15%, 17.34%, and 6.14%, respectively, indicating that ChCl–pTSA was selective for leaching Zn from Zn-containing dust sludge. The results of infrared spectroscopy showed that the characteristic peaks of Fe₂O₃ and Al₂O₃ in the leaching slag did not change significantly. In contrast, the distinctive peaks of ZnO gradually weakened and blue-shifted. The characteristic peaks of zinc in the leaching solution appeared at 480.66 and 1433.45 cm−1, indicating that the leaching of ZnO by ChCl–pTSA was mainly based on chemical interactions. On the other hand, the physical interactions of ChCl–pTSA with Fe₂O₃ and Al₂O₃ were dominant. XPS analysis showed that, in comparison to the zinc-containing dust, the characteristic peak orbitals of Zn in the leaching residue shifted, the characteristic peak area decreased, and the binding energy was reduced. In contrast, the characteristic peak areas of Fe and Al orbitals remained unchanged and did not undergo any apparent shifts. Molecular dynamics simulations showed that Zn mainly interacted with Cl and S ] O in the ChCl–pTSA ionic liquid via chemisorption during the leaching process.